acl/sinfonion

Sinfonion

Audiophile Circuits League

Complex harmonic CV processor combining three independent quantizer channels, a four-voice chord generator, an arpeggiator, and a chord progression sequencer, all sharing a common key and scale. Features 88 built-in scales, assignable CV and gate I/O, an input/output routing matrix, and Harmonic Link for connecting multiple units.987

Capabilities 4

Arpeggiatorarpeggiator
Arpeggiator with eight patterns, clock divider/multiplier, selectable range up to five octaves, and randomization CV.987
Chord Generatorchord-generator
Generates four-voice chords from selected scale notes with 98 voicings, spread, inversion, and optional CV control of voicing and spread.987
Quantizerquantizer
Three independent quantizer channels sharing a common key and scale, with per-channel note selection, optional triggered mode, bypass, slew detection, and equidistant quantizing on channel 3.987
Sequencersequencer
Chord progression sequencer storing 16 songs with 4 parts of up to 32 steps each; advances via clock, button, gate, or CV; sequences chord voicings, octave switches, and scale note selections.987

Jacks 32 (20 in / 12 out)

NameSignalVoltageDescription
Inputs (20)
ARP CLKclockClock input for the arpeggiator; each trigger selects the next note according to the current pattern. Normalled from the main sequencer CLOCK jack.987
Arpeggio INcv987
CH1 A/BgateDedicated gate input that switches Channel 1 between note-selection sets A and B when voltage exceeds approximately 3 V.987
CH1 INcv-10.24V to 10.24V987
CH1 TRIGtrigger987
CH2 INcv-10.24V to 10.24V987
CH2 TRIGtrigger987
CH3 INcv-10.24V to 10.24V987
CH3 TRIGtrigger987
CLKclockMain sequencer clock input; each trigger advances the sequencer by one beat. Normalled to the arpeggiator clock input.987
CV 1cv-10.24V to 10.24V987
CV 2cv-10.24V to 10.24V987
CV 3cv-10.24V to 10.24V987
CV 4cv-10.24V to 10.24V987
Chords INcv987
Chords TRIGtrigger987
IN 1gateGeneral-purpose gate input with 20 assignable functions including quantizer triggers, slew enable, arpeggio reset, sequencer control, and sync slave.987
Assignable destinations
Sync Slave987 Seq. Song Reset987 Seq. Step Forward987 Arpeggio Reset987 Chords Shuffle987
IN 2gateGeneral-purpose gate input with 20 assignable functions including quantizer triggers, slew enable, arpeggio reset, sequencer control, and sync slave.987
Assignable destinations
Seq. Song Reset987 Seq. Step Forward987 Arpeggio Reset987 Chords Shuffle987
ROOTcvDedicated CV input that shifts the root note; each 1/12 V (one semitone) changes the root by one step. Wraps around the full input range of ±10.24 V.987
TRANScvDedicated CV input for global transposition; tracks 1V/oct and shifts all eight pitch outputs together.987
Outputs (12)
Arpeggio OUTcv-2V to 8V987
CH1 OUTcv-2V to 8V987
CH2 OUTcv-2V to 8V987
CH3 OUTcv-2V to 8V987
Chords OUT1cv-2V to 8V987
Chords OUT2cv-2V to 8V987
Chords OUT3cv-2V to 8V987
Chords OUT4cv-2V to 8V987
GATE 1gate≤5V987
GATE 2gate≤5V987
OUT 1gateGeneral-purpose gate output with 14 assignable functions including autogates, arpeggio beat, sequencer clock/beat/step triggers, and sync master.987
Assignable destinations
Sync Master987 Autogate Ch1987 Arpeggio Beat987 Sequencer Clock987 Sequencer Beat987 Song Step987 Song Reset987
OUT 2gateGeneral-purpose gate output with 14 assignable functions including autogates, arpeggio beat, sequencer clock/beat/step triggers.987
Assignable destinations
Autogate Ch1987 Arpeggio Beat987 Sequencer Clock987 Sequencer Beat987 Song Step987 Song Reset987

Parameters 29

NameTypeRangeBehavior
Arpeggio Clockmenu_settingSets the clock divider/multiplier for the arpeggiator; 16 possible settings from 1/4 (divide by 4) to 4/1 (multiply by 4), including triplet ratios like 3/2. Default is 1/1.987
Arpeggio PITCHknobSets the pitch of the lowest note of the arpeggio pattern.987
Arpeggio RANGEknob0octave – 5octaveDefines the number of semitones from the lowest to highest arpeggio pitch. At zero it selects the closest note; up to five octaves of range is available.987
Arpeggio Trigger Delaymenu_settingDelays the arpeggio trigger to compensate for pitch-settling latency in a sequencer driving the arpeggiator pitch input.987
BEGINbuttonSelects the scale note at which the arpeggio resets and restarts; when set to Next Note the reset feature is disabled.987
Channel 1 A/Bmenu_settingSelects the criterion for switching Channel 1 between note-selection set A and set B: options include every odd beat, every odd clock, via the dedicated A/B jack, and others.987
Channel 2 Buttonsmenu_settingEnables single-note mode on Channel 2, where pressing any of the 12 interval buttons forces all others off so only one note is selectable at a time.987
Chords PITCHknobSets the overall base pitch of the chord section, equivalent to patching a CV into the Chords IN jack. Range covers four octaves.987
Chords RANGEknobControls the spread range of chord notes. When fully CCW the spread is minimal; turning right increases spacing between notes.987
Clock Dividermenu_settingDivides the sequencer clock input by a selectable factor (1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 16, 24, 32, 48, or 64). Saved per song part.987
DEGREEknobSelects the chord/scale degree within the current MODE, determining which specific scale is active. Combined with ROOT determines the complete scale shown on the display.987
Displaymenu_settingSelects what information is shown in the center of the display: Scale Tones, Scale Structure, Chord Structure, or Octave Switches.987
Intonationmenu_settingSelects the tuning temperament: equal temperament (default), just intonation (pure intervals, auto-retuned to current root), or quarter-comma meantone.987
INVbuttonCycles through chord inversions, forcing a specific chord tone as the lowest note, or setting free mode where the nearest tone above the input pitch is chosen as the lowest.987
MODEknobSelects among the named musical modes (Chords, Chords2, Slashch, Major, Minor, Mel.Minor, Har.Minor, Har.Major, Db.H.Maj), each providing up to 12 different scales accessible via the DEGREE knob.987
OCTbuttonToggles the OCT page overlay, where all 52 large buttons are remapped to octave switches and section options for each of the five sections.987
PATTERNbuttonCycles through eight arpeggio patterns: Up, Down, Up/Down, Down/Up, Baroque, Octaves, Brownian, Random.987
Pitch Bend Delaymenu_settingFades in the chords pitch bend after each chord change to create a delayed vibrato effect. Four settings: None (0 s), short (0.5 s), medium (1 s), long (2 s).987
POT 1knobAssignable potentiometer that can be mapped to any of the 28 CV functions via the menu, providing hands-on control without an external CV source.987
POT 2knobAssignable potentiometer that can be mapped to any of the 28 CV functions via the menu, providing hands-on control without an external CV source.987
PRESETknob1 – 16Selects one of 16 button presets in non-sequenced mode. In sequenced mode it becomes a song selector (1–16).987
ROOTknobSelects the root note of the global key/scale from all twelve chromatic pitches. Also adds to any CV applied to the ROOT jack when assigned.987
SEQbuttonActivates or deactivates the chord progression sequencer. When lit the sequencer is running and the PRESET knob becomes a song selector.987
SLEWknobSets the global slew (portamento/glide) time applied to enabled channels. When a CV is also assigned to Slew Time, this knob acts as an attenuator for that CV.987
Slew Curvemenu_settingSelects between linear slew (constant glide time regardless of pitch distance) and exponential slew (faster movement for larger intervals, like a capacitor-based analog slew limiter).987
SONGbuttonToggles the SONG page overlay (only active when sequencer is on), where buttons are remapped to song step navigation, part selection, and live mode toggle.987
TRANSknob-12semitone – 12semitoneGlobal transposition knob shifting all eight pitch outputs by -12 to +12 semitones relative to the current scale.987
Trigger Time Windowmenu_settingExtends the quantization window after a trigger edge so that sequencers with pitch-settling latency can be correctly sampled. Default 0 ms disables the feature.987
TUNEbuttonToggles tuning mode, which forces all eight pitch outputs to output exact integer-volt C notes and disables pitch-modifying CVs.987

Firmware history 1 version

VersionReleasedNotes
1.02019987

References 1

  1. [987]
    ACL Sinfonion Manual v1.0cmanual
    verified 2026-05-26